川裾拓也, 黒瀬築, 宮田 一司, 濱本 芳徳, 森 英夫, 並列ミニチャンネル内沸騰流の流量分配及び非定常流動現象に関するシミュレーション, 2017年度日本冷凍空調学会年次大会, 2017.09, A novel heat exchanger using parallel small refrigerant channels has recently been developed to improve the performance of air conditioning systems. However, for boiling flow in parallel channels, accurate prediction of heat transfer capacity is not easy because mass flow rates in respective channels tend to be non-uniform among them and/or oscillate. The authors have developed a simulation model which predicts the heat transfer capacity including the cases of non-uniformly distributed and oscillatory flows. In this paper, to confirm the validity of this model, the simulation for oscillatory flow occurred in parallel two mini-channels was compared with experiment. The simulation reproduced relatively well the oscillatory flow characteristics obtained by the experiment. Additionally, the simulation predicted flow rates in respective channels of the parallel channel under non-uniform heat flux condition..

4.

黒瀬築, 川裾拓也, 宮田 一司, 濱本 芳徳, 森 英夫, 不均一熱負荷並列ミニチャンネル内沸騰流に関する実験的研究, 2017年度日本冷凍空調学会年次大会, 2017.09, A novel heat exchanger using parallel small refrigerant channels has recently been developed for airconditioning systems. However, due to non-uniformly heat load among channels, boiling flow tend to be unevenlydistributed and become unstable in parallel channels. Since this uneven and unstable flow causes deterioration ofheat exchange performance, it is necessary to clarify the characteristics of boiling heat transfer in non-uniformlyheated parallel mini-channels. In this study, experiments on flow boiling in non-uniformly heated two parallelmini-channels were carried out and the characteristics of flow distribution and flow boiling heat transfer wereinvestigated. As the difference of heat flux between the two channels increased, the difference of flow rate betweenthem also increased. In a higher heated channel, flow rate was lower than average flow rate of the two channelsand heat transfer coefficient decreased..

宮田 一司, 齋藤 正士, 森 英夫, 濱本 芳徳, 管内の非定常沸騰流に関するシミュレーション, 2016年度日本冷凍空調学会年次大会, 2016.09, A novel heat exchanger using parallel small refrigerant channels has recently been developed for air conditioning systems. Boiling flow in parallel channels is, however, subject to unstable flows. The unstable flows trigger dryout even under low time-averaged quality conditions and result in deterioration of heat transfer capacity of the heat exchanger. The authors developed a simulation model which predicts heat transfer capacity of the parallel channel heat exchanger under unstable boiling flows. In this paper, to confirm applicability of the model, the simulation results for pressure drop oscillation and density wave oscillation in a single channel tube were presented and compared with the conventional experiments. The simulation model reproduced well the periodical changes of mass flow rate and pressure drop in the pressure drop oscillation and stability boundary for the density wave oscillation..

10.

宮田 一司, 齋藤 正士, 森 英夫, 濱本 芳徳, 並列ミニチャンネル内沸騰流の流量変動現象に関するシミュレーション, 2016年度日本冷凍空調学会年次大会, 2016.09, A novel heat exchanger using parallel small refrigerant channels has recently been developed for air conditioning systems. Boiling flow in parallel channels is, however, subject to unstable flows. The unstable flows trigger dryout even under low time-averaged quality conditions and result in deterioration of heat transfer capacity of the heat exchanger. The authors developed a simulation model which predicts heat transfer capacity of the parallel channel heat exchanger under unstable boiling flows. In this paper, to confirm applicability of the model, the simulation results for flow oscillation in two-parallel channels were presented and compared with the conventional experiment. The simulation model reproduced well the characteristics obtained from the experiment. Additionally, heat transfer rate under flow oscillation was simulated, and the result that periodical dryout lower the heat transfer rate was obtained..

宮田 一司, 森 英夫, 大石 克巳, 濱本 芳徳, Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing in a Vertical Small Diameter Tube, KAIST Kyushu University Joint Seminar, 2008.09, In the present study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing in a vertical copper smooth tube with 1.0 mm inside diameter. Local heat transfer coefficients were measured in a range of mass fluxes from 30 to 200 kg/(m2•s), heat fluxes from 1 to 16 kW/m2 and qualities from 0 to 1 at evaporation temperature of 10°C. Pressure drops were also measured at mass fluxes of 100 and 200 kg/(m2•s) for upward flow and of 30, 50, 100 and 200 kg/(m2•s) for downward flow and qualities from 0.1 to 0.9. Three types of flow pattern were observed in the tube: A slug, a slug-annular and an annular flow. Based on the measurements, the characteristics of frictional pressure drop, heat transfer coefficient and dryout qualities were clarified..

20.

宮田 一司, 森 英夫, 大石 克巳, 濱本 芳徳, 三角形細管内垂直下降流の沸騰熱伝達と圧力損失, 日本伝熱シンポジウム, 2008.05, In the present study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically downward in a copper triangular tube with 0.88 mm hydraulic diameter for the development of a high-performance heat exchanger using small channel tube for air conditioning system. Their characteristics were clarified by comparing the measurements with the data for small diameter circular tube and rectangular tube flow previously obtained..

21.

宮田 一司, 森 英夫, 大石 克巳, 濱本 芳徳, 矩形細管内垂直上昇流の沸騰熱伝達と圧力損失, 日本冷凍空調学会年次大会, 2007.10, In the present study, experiments are performed to examine characteristics of flow boiling heat transfer andpressure drop of a refrigerant R410A flowing vertically downward in a copper rectangular tube with 1.0mm on a sidefor the development of a high-performance heat exchanger using small channel tube for air conditioning system. Theircharacteristics were clarified by comparing the measurements with the data for small diameter circular tube flowpreviously obtained..

22.

宮田 一司, 森 英夫, 濱本 芳徳, 大石 克巳, 垂直細管内流の沸騰熱伝達と圧力損失, 日本伝熱シンポジウム, 2007.05, Experiments were carried out on boiling heat transfer and pressure drop of a refrigerant R410A flowing downward inside a copper smooth tube of 1.0 mm I.D. for the development of a high-performance heat exchanger using small diameter tubes for air conditioning systems. In addition, two-phase flow patterns were observed. Heat transfer and pressure drop characteristics were clarified based on the data, comparing with upward flow data obtained previously..

23.

宮田 一司, 松尾 良平, 大石 克巳, 森 英夫, 垂直細管内上昇流の沸騰熱伝達と圧力損失, 日本冷凍空調学会年次大会, 2006.10, In the present study, experiments were performed on boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward inside a copper smooth tube of 1.0 mm inside diameter for the development of a high -performance heat exchanger using small diameter tubes for air conditioning systems. Based on the obtained data their characteristics were clarified and the results of observation of two-phase flow pattern were shown..